Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$226.48	6.457%	$241.1038	$241.10	$241.10	$241.10
Purchase #2	$211.34	10.493%	$233.5159	$233.52	$233.50	$233.50
Purchase #3	$229.95	12.587%	$258.8938	$258.89	$258.90	$258.90
Purchase #4	$119.55	6.841%	$127.7284	$127.73	$127.75	$127.70
Purchase #5	$41.44	10.440%	$45.7663	$45.77	$45.75	$45.80
Purchase #6	$96.60	11.510%	$107.7187	$107.72	$107.70	$107.70
Purchase #7	$68.53	9.324%	$74.9197	$74.92	$74.90	$74.90
7 purchase totals =	$993.89		$1,089.6466	$1,089.65	$1,089.60	$1,089.60